Apparatus for television transmission and reception



Feb. 10, 1942. w. H. HICKOK APPARATUS FOR TELEVISION TRANSMISSION AND RECEPTION Filed Sept. 26, 1940 2 Sheets-Sheet l INVENTOR SAW 7'00 TH MODULA T/ON SOURCE Feb. 10, 1942. w. H. HICKOK APPARATUS FOR TELEVISION TRANSMISSION AND RECEPTION Filed Sept. 26, 1940 2 Sheets-Sheet 2 TEL EVE/0N RECEIVER nvwszvroa (LLARD H. HICKOK Patented Feb. 10, 1942 APPARATUS FOR TELEVISION TRANS- MISSION AND RECEPTION Willard n. Hickok, Bloomfield, N. 1., assignor to Radio Corporation of America, a corporation of Delaware Application September 26, 1940, Serial No. 358,437

8 Claims.

My invention relates to apparatus for transmitting and receiving television images of panoramic views and particularly to electronic devices for such use.

In the televising of panoramic scenes it has been customary in the art to use a single camera mounted on a support and capable of rotation about a vertical axis whereby a succession of images representative of a moving panoramic view are transmitted and received as a moving panoramic view at the receiving location. In such a system the transmitting tube is directed at successive points on the horizon and is incapable of viewing all points on the horizon simultaneously.

It is an object of my invention to provide a television transmitting tube and system whereby a continuous unbroken view of the horizon and intermediate objects may be transmitted simul- I image screen may be used at both the transmitting and receiving locations for transmitting and receiving a continuous panoramic image. It is another object of my invention to provide a television transmitting tube of the cathode ray type wherein full storage of the panoramic image replica may be obtained during the time required for electron analysis of the elemental areas of the image, and it is a still further object to provide a tube and system of the type described wherein the orientation of the panoramic image at the receiving location is similar to the orientation of the original panoramic view.

In according with my invention I provide a novel television transmitting system and tube of the electron beam scanning type having a target electrode on which may be focused a plurality of optical images of successive and,

tages of my invention will become apparent when taken in connection with the following description and the accompanying drawings in which: 1

Fig. 1 is a longitudinal perspective view of a television transmitting tube and associated circuit made in accordance with my invention,

Fig. 2 is a cross-section of the tube shown in Fig. 1 taken along the lines 2 2 showing a portion of an optical system suitable for use with my tube,

- Fig. 3 is a view of a scanning rasterof a conventional television receiving tube showing loss of a portion of'the recreated image.

Figs, 4 and 5 show two types of television receiving tubes suitable for recreating panoramic images, and

Fig. 6 is a View of the scanned target of the tube shown in Fig. 5.

Referring to Fig. 1, my television transmitting tube comprises an evacuated envelope I which is preferably of cylindrical form, having at one end a conventional-type electron gun 2 including a cathode, a control electrode and a first anode to develop an electron beam. The electron beam is directed axially of the envelope I through two pairs of conventional deflection plates 3-4, 5-6. In accordance with my invention I provide a light sensitive target electrode 1 such as a photosensitive target of mosaic formation in the form of an open-ended cylinder in combination with a symmetrically disposed electron collecting electrode 8 supported axially of the cylindrical target.

The mosaic electrode 1 may be fabricated in the same manner as for conventional planartype electrodes and preferably comprises a thin rectangular sheet of mica l9 bent to form a cylindrical surface with the opposite edges of the sheet of mica contacting one another. One side of the mica sheet In which is to be the outside of the cylinder, that is, the side facing outwardly from the cylindrical axis, is provided with a translucent or semi-transparent metal film ll, the opposite side of the mica sheet l0, that is, the side facing the axis of the cylinder, being provided with an exceedingly great number of mutually separated photosensitive particles, the area covered'by the particles being coextensive with the metal film H. The metal film II serves as a signal electrode and is connected to an output circuit as described later.

In making the target or m'osaic electrode 1 select the mica sheet [0 of the desired area such that upon being bent or rolled it will form a cylinder of the desired diameter, and as a first step, coat one side of the mica sheet with a film of metal of sufficient thinness as to be substantiallytransparent so as to transmit light through the sheetof mica and upon the side of the sheet facing the axis of the cylindrical target. The deposition of'a metal such as platinum or palladium by evaporation and condensation or by sputtering has been found very satisfactory for this purpose. On the opposite side of the sheet from the film II I provide a great number of mutually separated particles which may be deposited on this surface of the mica sheet as finely divided silver oxide which is reduced to provide a surface of individually separated silver globules or particles I2. The silver particles may be formed also by an evaporation process followed by baking to break the deposited silver film into the small particles. The particles I2 are subsequently oxidized and sensitized with an alkali metal such as caesium during the evacuation process. Following the formation of the metal film II and mutually separated particles I2 on the mica sheet, the sheet may be bent or rolled to form the cylindrical target with the particles I2 facing the axis of the target cyl inder, and the edges of the mica sheet may be either butted together or overlapped to provide rigidity. The mosaic electrode target so formed is inserted in the envelopel such as prior to sealing the end wall of the envelope to the cylindrical portion of the envelope and supported with its axis coincident with the axis of the electron gun 2.

The electron collecting electrode 8 extends axially of the tube and preferably beyond each end of the cylindrical target I as shown in Fig. 1.

To insure an electrostatic field-free space andfurther to.focus the electron beam on the target I I provide an electrode or second anode I3 in the form of a wall coating extending from a point in the neck section of the envelope closely adjacent the electron gun anode to a point on the cylindrical section of the envelope I adjacent the target I, although the electrode I3 may be excharge image of the various optical images which is representative of the panoramic view to be televised. The electrostatic charge image is then electronically analyzed to generate signals proportional to elemental areas of the light and shade intensity of the panoramic optical image.

Referring again to Fig; 1, the electron beam generated by the gun 2 is projected axially of the tended in overlapping relationship with the cylindrical target I, provided the diameter of the cylindrical portion of the envelope I is suflicient to minimize capacitance effects between the electrode I3 and the signal electrode metal film II. The electron collecting electrode 8 and second anode I3 are preferably maintained at the same potential such as ground and at a positive potential with respect to the cathode of the electron gun by a battery or potential source I4, while the signal electrode or semi-transparent metal film II is connected to an amplifying device I5 and to ground throughan out-put impedance I5.

Referring to Fig. 2 prior to a further consideration of the circuit shown in Fig. 1, optical images such as represented by the arrows II are focused by the lens systems I8 through the semi-transparent metal film II and upon the photosensitive mosaic particles I2 to form contiguous upright images of the panoramic view to be televised. It will be obvious that the optical Systems represented by the lens systems I8 are preferably equally spaced and provided around the periphery of the cylindrical target I so that the composite image focused on the photosensitive particles is formed by separate images adjacent one another in. such a manner that the entire image on the photosensitive particles is a continuous image of the horizon and intermediate objects. The light representative of the panoramic view when focused on the photosensitive particles I3 liberates photo-electrons which are uniformly collected by the collecting elecztrode 8, thereby producing an. electrostatic envelope I and cylindrical target I and deflected by the two pair of deflection plates 3-4, 5-6 to spirally scan the interior surface of the cylindrical target I. It is well known in the cathode ray tube art that if sine-wave potentials having a 90 phase displacement are applied to two pairs of plates with the plates of one pair mutually perpendicular to the plates of another pair, circular scanning of the electron beam results. In accordance with my invention I apply a sinewave potential between the deflection plate 3 and the grounded plate 4 of the first pair of plates and a second sine-wave potential to the deflection plate 5 with respect to the grounded plate 6 of the second pair, the latter potential being displaced in phase from the former by 90 Furthermore, I simultaneously modulate the amplitude of both of the sine-wave potentials to vary the amplitude of the scanning, whereby the electron beam is made to progressively scan the cylindrical target 1 from one end thereof to the other while simultaneously describing curved paths around the cylindrical target. The combination of the amplitude modulation applied to the sine-wave potentials produces a spiral scanning of the inner surface of the target I. Simultaneously with the spiral scanning of the target I I vary the focus of the electron beam so that the diameter of the electron beam impinging on the target I is substantially invariable as it sweeps from one end to the other of the target.

Referring more particularly to the circuit shown in Fig. 1, I provide a sine-wave oscillator 20 to generate a sine-wave of the desired frequency. For example, assuming the transmission to be at a standard of 441. lines at 30 frames per second, the oscillator 20 is then designed to provide a sine-wave potential at a frequency of 13,230 cycles per second. The amplitude of this sine-wave potential is then modulated from a source of sawtooth potential 2I such as by a modulating tube 22 whose input is connected to the source of sine-wave potential such as the oscillator 20 and to the source 2I of sawtooth potential having a frequency of 30 cycles per second. Obviously, interlacing of the'pattern may be provided by applying a proper multiple of 30-cycle sawtooth oscillations to the modulator 22. The output of the modulator 22 is applied to a phase displacement network 23-24 and thence through amplifiers 25-26 to the plates 3 and 5 to provide the spiral scanning of the target I. Simultaneously with the scanning through the connections 21-28. The means or V photosensitive particles I2 of the target I- produces a flow of secondary electrons proportional to the light intensity on elemental areas of the target 1, the secondary electrons being uniformly collected by the electrode 8, since it is supported axially of the target I. It is therefore obvious that the secondary electron emission is efliciently collected, since the electrode 8 is equidistant from all of the photosensitive particles I2. Consequently, if the electron beam is scanned over the photosensitive particles l2, a voltage impulse will be applied across the output impedance by condenser action between the photosensitive particles i2 and the semitransparent metal film II, the voltage impulses being amplified and applied to a transmitting network such as through the amplifier l5, as well known in the art. Synchronizing impulses may likewise be applied to the transmitting network to controlthe mechanism of scanning at the receiver location.

The reception of television signals is well understood in the art and the signals representative of the panoramic view being televised may be applied to a conventional cathode ray receiving tube synchronized with the transmitter and utilizing rectangular scanning coordinants. However, signals generated by a transmitting tube made in accordance with my invention and representative of a panoramic view cannot be recreated in their entirety by the use of rectangular scanning coordinants at the receiver location. This is due to the fact that as the scanning beam traces parallel lines to form a rectangular raster, the finite return time of the electron beam to the initial point of line formation causes some loss of the signal information because in my system the information is transmitted continuously except for the exceedingly short time required for the electron beam in the tube of Fig. 1 to return to its initial longitudinal position for rescanning the cylindrical target. Consequently, if the horizontal line return time at the receiver occupies 5% of the horizontal line time, the panoramic View capable of being received will be discontinuous. Thus one portion, or 18 of the 360 view, will not be received. Therefore, in accordance with my invention I prefer other modes of scanning at the receiving location than the conventional scanning in rectangular coordinants.

Complete reconstruction of the televised panoramic image may be obtained in accordance with my invention in a tube of the type shown in Fig, 4 which is a tube quite similar to the tube shown in Fig. 1 except that it is designed for television receiving purposes. Referringto Fig. 4, the tube comprises an evacuated envelope preferably of cylindrical form and having a neck section enclosing an electron gun 3| including a cathode, control electrode, and one or more anodes. The electron beam is developed and directed toward and scanned over a cylindrical target 32 which may be a coating of luminescent material on the interior surface of the cylindrical envelope portion by deflection means such as the deflection plates 33-34, 3536. comprise a thin film or layer of luminescent material such as zinc-beryllium silicate, various sulphide phosphors, or mixtures of these materials to obtain any desired color of light output. Iri accordance with my invention the electron beam is deflected by applying sine-wave potentials having 90 phase displacement to the two pairs of deflection plates 33-34, 3536 while simultaneously varying the amplitude of the sine-wave potentials to produce spiral scanning More particularly, the target 32 may on the target 32, and simultaneously with the spiral scanning varying the focus of the electron beam in accordance with the amplitude modulation applied to the sine-wave potentials so that the electron beam is properly focused over all elemental areas of the target as explained in connection with Fig. 1. A television receiving tube made and operated in accordance with this teaching of my invention produces a con inuous replica of the panoramic image or images focused on the target of the tube of Fig. 1 and, consequently, no portion of the recreated image is lost as in the case of rectangular scanning described above.

Further in accordance with my invention and referring to Figs. 5 and 6, the receiving tube target may be of the planar or substantially planar form comprising an annular ring of flucrescent material 40 which is spirally scanned by the electron beam as shown in Fig. 6 such as from the point 4! adjacent the outer periphery of the annular target to a point 42 on the inner periphery of the target. The scanning of the target 40 shown in Fig. 6 is synchronous with respect to the scanning of the target I of Fig. 1. It will be apparent that the linear velocity near the outer periphery of the target 40 will be greater than the linear velocity of scanning adjacent the inner periphery of the target such as at the point 42. Consequently, there will be a constant decrease in the linear velocity of the electron beam as the target is spirally scanned from point M to point 42. The image information portrayed by the electron beam and representative of the optical image being transmitted will not be lost, but will be merely condensed so that a portion of the entire panoramic image will be wedge-shaped such as shown by the dashed lines 43. Obviously the effect of crowding the recreated image replica adjacent the inner periphery of the target 40 may be minimized by providing an annular target with a larger mean diameter.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without cleparting from the scope of my invention as set forth in the appended claims.

I claim:

1. Television transmitting apparatus comprising an evacuated envelope, an electron gun to develop an electron beam, a beam receiving target positioned to be scanned by said beam and to have an optical image for transmission focused thereon, said target having a closed cylindrical light sensitive surface, an electron collecting electrode exposed to and substantially axially concentric with said surface to collect electrons liberated from said target and means toscan said beam over the surface of said target which is exposed to said collecting electrode.

2. Television transmitting apparatus comprising an evacuated envelope, an electron gun to develop a beam of electrons, a cylindrical light sensitive target having a surface of revolution about the normal undefie'cted path of said electron beam, means to deflect the beam over the inner surface of said target and an electron collecting electrode located along the axis'of said cylindrical target.

3. Television transmitting apparatus including a cylindrical target electrode, means on the inner cylindrical surface of said target to liberate electrons in response to a plurality of displaced optical images focused thereon, an electron collecting electrode symmetrically disposed with respect to said means along the axis of i said cylindrical target, means to generate an electron beam and means to deflect said beam over the inner cylindrical surface of said target to generate signals representative of said displaced optical images.

4. Television transmitting apparatus including a cylindrical open-ended mosaic electrode foundation, a discontinuous coating of photo-elec trically sensitive mosaic particles on theinner cylindrical surface of said foundation, a thin substantially transparent coating of electrically conducting material on the exterior cylindrical surface of said foundation, an electron collecting electrode substantially equidistant from said photo-electrically sensitive particles along radii of said cylindrical foundation, means to generate an electron beam and means to scan said beam over the photosensitive particles on the inner cylindrical surface of said foundation.

5. Television transmitting apparatus including a tube having a hollow cylindrical light sensitive target and means to generate and project an electron beam having a substantially constant longitudinal velocity along the axis of said tar-get, means to sweep said beam over a closed circular path on said target, means to displace the point of impingement of said beam on said target in a direction normal to said circular path without substantially altering the longitudinal velocityof the electrons of said beam to scan elemental areas on said target displaced longitudinally along the axis of said target and means to simultaneously vary the focus of said electron beam in accordance with the longitudinal progression of said beam over the length of said cylindrical target.

6. Television transmitting apparatus including an electron gun to focus a beam of electrons upon an elemental area of said target, an electron collecting electrode coaxially supported within said. target, and two pairs of mutually perpendicular deflection plates to sweep said beam over said target, means to apply to one pair of said deflection plates a sine-wave potential,

D means to apply to the other pair of deflection a tube having an open-ended cylindrical target,

plates a sine-wave potential having a phase displacement with respect to 'said first-mentioned potential, means to modulate said sinewav potentials with a sawtooth potential to vary the amplitude of deflection of said electron beam and means to simultaneously vary the focus of said electron beam in accordance with the said sine-wave potential.

'7. Television transmitting apparatus including a transmitting tube having a cylindrical charge storage target electrode, means to focus on said cylindrical target simultaneously a plurality of continuous optical images displaced one from the other around the circumference of said cylindrical target, the said plurality of images being representative of a panoramic scene to be televised to generate an electrostatic charge image representative of said scene, and means to scan said target with its electrostatic charge image with a beam of radiant energy to sequentially discharge elemental areas of said charge image.

8. Television apparatus including a transmitting tube having a cylindrical target electrode, means to form a plurality of contiguous optical images on said target electrode representative of a panoramic scene to be transmitted, means to generate a beam of radiant energy and means to scan said beam over said target to develop 'signal impulses representative of said scene, a

receiving tube having a cylindrical target on which a replica of said optical images representative of said scene may be recreated, means to develop a beam of radiant energy to scan said cylindrical target, means to scan said beam of radiant energy over said target and means to modulate said beam of radiant energy in accordance with the said signal impulses.

WILLARD H. HICKOK. 

